Can someone help with this section

When could you attach the direct object pronoun to an infinitive verb? a: when an infinitive verb follows a conjugated verb. b: when an infinitive verb ends in a question. c: when a stem-changing verb ends in a question. d: when a stem-changing verb follows a conjugated verb.

La lengua de los inca y de muchos peruanos indígenas es a. el español c. b. el inca d. el quechua el ande

Units for measuring liquid capacity